(I) The history of manned space flight has been marred by a number of tragic accidents involving the early spacecraft (II) They were comparatively small, weighing only a few kilograms, and performed no useful scientific experiments. (III) Nevertheless they served as proof that mankind had the means to place objects in the sky, outside the Earth's atmosphere, and to keep them there. (IV) There are now a considerable number of artificial satellites at distances varying between several hundred and several thousand kilometres above the surface of the Earth. (V) They have become highly sophisticated, and perform functions from weather forecasting to home entertainment.